How to get rid of loop?
Ken-JP wrote:
The code below shows what I'm trying to get rid of. If there is no way to get rid of the loop, I will try to use package( inline ). I'm just curious as to whether there is a "vector way" of doing this algorithm.
I don't see a vector way. If speed is an issue, I'd suggest to port this small part to C, it's very simple and may yield a considerable performance boost (untested). It can probably be used as a textbook example for code where porting to C make sense. Best, Uwe Ligges
#
-----------------------------------------------------------------------------------------
set.seed(1)
x <- runif(100)
n <- length( x )
y <- rep(NA, n)
yprev <- 0;
for ( i in (1:n)) {
if ( x[i]>0.75 ) {
y[i] <- 1;
} else if ( x[i]<0.25 ) {
y[i] <- -1;
} else if ( yprev==1 & x[i]<0.5) {
y[i] <- 0;
} else if ( yprev==-1 & x[i]>0.5) {
y[i] <- 0;
} else {
y[i] <- yprev
}
yprev <- y[i];
}
y
[1] 0 0 0 1 -1 1 1 1 1 -1 -1 -1 0 0 1 0 0 1 0 1 1 -1 0 -1 -1 [26] -1 -1 -1 1 0 0 0 0 -1 1 1 1 -1 0 0 1 1 1 1 1 1 -1 -1 0 0 [51] 0 1 0 -1 -1 -1 -1 0 0 0 1 0 0 0 0 0 0 1 -1 1 0 1 0 0 0 [76] 1 1 0 1 1 0 0 0 0 1 -1 0 -1 -1 -1 -1 -1 0 1 1 1 0 0 1 1